I'm close to solving an electrical problem...

[Jack Olsen]

...but my utter lack of knowledge on the subect has me stumped.

I have a radar detector and an iPod. For long trips, I've worked out a scheme where I have both devices feed into the same audio line through this passive mixer. It works.

Sort of.

If I'm simultaneously charging the iPod from the car's power supply, I get a rhythmic humming sound on the line. I tried isolating the power of each device to different regulated circuits in the car, and it had no effect. I tried running them off of the exact same regulated power source in the car, to no effect. I tried running both of them off of a 12V battery, and the flippin' hum was still there.

I can listen to the iPod off its battery and have the V1 signal piped in through the mixer, and everything's fine. I can listen to the iPod while it's charging, but without the V1 plugged in, and it's fine. But I can't do both at the same time.

I'm hoping an exotic device called a 'diode' is going to save me. But again, I'm dumb as a box or rocks when it comes to volts, amps and watts.

Can anyone help? The long trips where I most need to hear the V1 are also when I most need to run the iPod off of the car's power.

(I got a speeding ticket in my other car yesterday, so the problem is even more urgent.)

[FrayAdjacent911]

I don't think a diode will do much. You probably have alternator noise coming through the power circuit. You could probably find an audio filter, which is some sort of capacitor, that should cut down on the noise.

Does the humming change pitch/frequency with your engine revs?

[Jack Olsen]

No, it's pretty constant. And like I said, powering both from a 12V battery that is not connected to the car produces the same result.

Could a capacitor function like a gate, stopping the hum, but still allowing the tone signal (which I presume is stronger) through?

[H20911]

beat me too it. the diode is just a one way elctrical valve that cuts off in an alternator the non positive portion of a sinewave so you get a a pulsed positive to charge with.
You might need a noise filter instead to solve your issue.
One of the most famous uses for a diode is when MSD ignitions keep running the engine after the car is shut off. the diode is used for a bleed back shut off from the alternator.

[david914]

Jack, not owning a V1 I can't speak to the design of the V1 power supply, but I suspect that's the culprit. In simplest terms, your reference to a diode is not far off. I suspect the common ground between the V1 and the IPOD is causing a ground loop, which in turn is creating the interference. What you need to do is isolate your V1 from your IPOD electrically. The common thread being your mixer. If you were to use an isolation transformer (to electrically separate the V1 ground from the IPOD) between the V1 output and the mixer, that should take care of the problem. I can do a little digging and find some suitable suggestions if you like. I imagine there are others here that may know right off the bat.

[H20911]

Call Mike and ask. I tried and they are closed for the day (close at 530pm). He would be the one to ask.
http://www.valentine1.com/lab/
1.800.331.3030

[david914]

Jack,
Just had a quick look at your mixer's website. They sell what I was referring to. Look here http://www.accessoryworkshop.com/products/isolator_cables.htm

[rattlsnak]

Sounds like you need a condensor. It absorbs RFI and shunts it to ground.

[ZOA NOM]

It's those monster tires, Jack. Turn up the volume!

[RoninLB]

I sure there's a contraption that could be installed for a fix.

I'd not interchange the 2 systems in any way.. especially with grounds or power. I base this prejudical response on my beliefs that 911 elec systems suck to begin with.

[ed martin]

I think we're talking about electromagnetic radiation (radio waves) and finding an appropriate filter. I know that Radio shack has a filter for phones to eliminate humming in my phone line( it filters out EMF from a nearby transmitting tower) The filter is essentially a coil that will absorb certain electromagnetic frequencies. The principle is the same in your situtation if I'm not mistaken. The trick I suppose is to find the appropriate coil for the frequency emitted. Try radio shack or some electronic specialty store, they may have a solution for you.

[RoninLB]

Originally posted by Jack Olsen
[BI can listen to the iPod off its battery and have the V1 signal piped in through the mixer, and everything's fine. I can listen to the iPod while it's charging, but without the V1 plugged in, and it's fine. But I can't do both at the same time.

[/B]

I'm curious.. how do you you have the V-1 piped in ?

[bell]

jack..... you need to "change" the ground path of the audio signal to isolate the ipod.
did you try running a separate ground wire for both the v1 and the ipod for their power supplies?
you can try grounding the rca inputs ground shield for the ipod, simply wrap a wire around the outer terminal of the rca and touch to ground, if that doesn't work i have about 5 other possible simple remidies......
but i've gotta get to work, i'll be back online tonite to check your progress.
later

[Jack Olsen]

Thanks, guys. It looks like I need to get the cable the company that makes my mixing box sells. I hadn't looked at anything else on the mixing box's website, but it looks like this same problem has reared its head for other users.

Originally posted by RoninLB
I'm curious.. how do you you have the V-1 piped in ?

I bought the remote audio control for the V1, which has a plug for headphones (I guess motorcycle guys use it) or an additional speaker. It runs into the mixing box, along with the iPod audio, and then I plug my headphones into the box.

[RickM]

Would I use one of these mixers if I want to share a cell phone headset with an Ipaq (to listen to gps instructions) or would I be better with an A/B switch?

Don't mean to hijack the thread, just seems appropraite to ask here.

[Jack Olsen]

Yes, that's what they're designed for. You can get one with two mono inputs (radar detector, GPS navigation) and one stereo input (music). Motorcyclists use them for this stuff, as well as Nady/chatterbox-style communicators.

[RickM]

Great. I was recently wondering what the most elegant solution would be. Thanks!

[RoninLB]

Originally posted by Jack Olsen

I need to get the cable
same problem has reared its head for other users.

remote audio control for the V1,
. It runs into the mixing box,

good ending.. elec piping fixes are good&relaxing imo.
It's better than some elec contraption that only cleans up the prob and leaves behind .75+

your V-1 remote info is what I got from V-1 tech to push an amp. I have two Focal tweeters that should push the V-1's 2kHz cleanly at big db w/a cheap radio shack.. it's only another bright idea.

[HawgRyder]

Jack: You can try using "Ferrite" beads on the power lines to each unit.
The beads will take out RF interference from the DC power lines.
It sounds like the Valentine is pushing something back into the power circuit that is being amplified by the iPod.
If you get the snap on variety of ferrite...you don't have to break the line to slide it on...they just fold onto the wire.
Get the correct ones for the diameter of the wire and do the hot and ground together.
Bob

PS...is everything else electrical still working OK?

[RoninLB]

Originally posted by HawgRyder

You can try using "Ferrite" beads on the power lines to each unit.

nice info.

I've never seen this "beads" used so I did a google and found this

http://www.antennex.com/shack/Dec99/beads.htm

" An alternative approach is to use ferrite beads to reduce the amount of RF entering the equipment. "

"Ferrite beads just slip over the wires and stop RF from going in."

"The beads, unlike a resistor, do not affect the wire at low frequencies so the audio, DC, and other low frequency components go through the wire just as though the bead were not there."